Storage library systems are often used by enterprises and the like to efficiently store and retrieve data from storage media. In the case of some storage libraries, the media are data cartridges (e.g., tape cartridges) that are typically stored and indexed within a set of magazines. When particular data is requested, a specialized robotic mechanism finds the appropriate cartridge, removes the cartridge from its magazine, and carries the cartridge to a drive that is designed to receive the cartridge and read its contents. Some storage libraries have multiple drives that can operate concurrently to perform input/output (IO) operations on multiple cartridges.
Operation of the robotic mechanism in the context of a data storage system, typically involves a number of different location related tasks. For example, the robotic mechanism may be used for targeting of specific locations within the data storage system, for performing pick and place operations on media cartridges, for reading barcodes and/or other symbols or features, for auditing the existence and/or absence of media cartridges in magazines or drives, etc. Each of these and other operations can be frustrated when location-related errors are introduced into the environment, if proper corrective feedback is not provided. For example, errors can easily be introduced into the system from physical jarring or manipulation of components, from compounding of errors inherent in electronic components, etc.
Many different techniques are used in an attempt to account for these errors and to accurately locate, or determine the location of, the robotic mechanism or its constituent features in the context of the storage library. Various implementations use stepper motors, physical stops, electromechanical sensors, electro-optical sensors, and/or other techniques. For example, the carriage may move until it detects via one or more sensors that it has reached a desired location. Traditional implementations use a number of different sensors and other location and feedback techniques to provide all the different functionality desired from the robotic mechanism, including scanning and location-related tasks. This may involve integrating large numbers of components, which can add complexity, cost, and weight, while also potentially increasing the rate of failure.